If there is current flowing in the primary circuit, the secondary circuit should never be opened. Due to the amp-turns of the primary that begin magnetizing the core, this can result in extremely high voltages. It will create very high voltage peaks while serving as a transformer... These high voltage spikes could damage any devices connected to the secondary side of the transformer.
The secondary side of a transformer should only be used for light load situations or when an overload protector is not needed. Connecting heavy loads to the secondary side of the transformer can cause damage to these items too. Transformer secondary circuits should always be kept simple - just like their primary sides.
The secondary side of a transformer should also not be left open when the primary is closed. This would allow any energy stored in the primary side of the transformer to flow directly into the earth ground. This could cause serious problems if enough power was allowed to flow through the secondary when the primary was closed!
Finally, both sides of the transformer must be grounded. This is necessary because all electrical components contain some amount of resistance which will draw some current even when they are off. This current will flow through anything else with a lower resistance path to ground.
As a result, the core is saturated for a significant amount of the cycle. This means that it will not readily revert back to its original state if forced.
The secondary side of a transformer must always be closed when the primary is open. Otherwise, you will get very high voltage levels on the secondary side which could cause damage or kill someone.
The only time this would be acceptable is if the power company automatically opens your circuit after any major power outage so they can check on any homes that may have lost their power. But even then, your circuit should only be opened for a short period of time.
Otherwise, you should always wait for electricity to be restored before opening the secondary side of the transformer.
There is an open circuit in a CT secondary. These high voltages could damage electrical components on the vehicle.
If you ever see any green or red lights on your driver's side door lock with the engine off, this means that someone has opened the door without using the key. If you want to protect yourself from being locked out of your car, always use your key fob or phone app to unlock your door. This way, you will be able to get back into your car even if you had your seat set to its full upright position.
Opening a CT secondary circuit may also cause excessive wear on other components such as relays and contactors. In this case, the component will fail prematurely due to overloading. Overloaded components require more power than normal to operate properly. This increased demand for power causes further overloads that can lead to failure of other components. This form of component failure is called "component cascade" and can result in extensive damage to your vehicle's electrical system.
To prevent unnecessary strain on your electrical system, do not open any doors of your vehicle who's engine is off.
To avoid core saturation and high voltage induction, the secondary side of the current transformer is constantly kept short-circuited, allowing the current transformer to monitor high current values. This configuration ensures that the transformer does not saturate and fail prematurely.
An open circuit in a current transformer (CT) might cause a severe overvoltage condition at the CT's secondary terminals. An open circuit CT, especially one with a high ratio and carrying a large current, can create a secondary open circuit voltage in the kilovolt region. This is usually enough energy to start a fire or damage electrical equipment.
The following images show what happens when you open circuit a CT:
Figure 1. A CT without power will decay to an unloaded state within about 100 hours. Powering up the unit after this time will result in the creation of a dangerous voltage across its windings.
Figure 2. An open circuit on a CT causes a destructive voltage to appear across the winding. If left unattended, this voltage will destroy the insulation on the wire and lead to further short circuits.
Figure 3. When loading a CT while it is off-line, there should be no voltage across its windings. If there is, then someone has opened the circuit incorrectly and must not do so again!
Figure 4. When removing the load from a CT while it is off-line, the voltage across its windings should disappear. If it does not, then someone has opened the circuit incorrectly and must not do so again!
Current transformers should always be shorted across the secondary terminals unless a load (e.g., meters, relays, etc.) is attached to the CT. Because of this, extremely high voltages will be induced at the terminals. These high voltage levels could damage the load if it were not protected by a fuse or circuit breaker.
The purpose of shorting current transformers across their secondary side is to prevent excessive voltage from developing on the primary side. This keeps mechanical damage and electrical failure to a minimum. Current transformers used in power systems must be designed to withstand high voltages without damage. The way they do this is by using insulation around its core and windings. This prevents any contact between the metal parts of the transformer and its core or coil windings.
If current transformers are not shorted across their secondary side, an extreme voltage may develop which could cause damage to the load itself or other components in the system. For example, an unprotected CT might reach 1500 volts when energized with 240 VAC from a hot wire on a motor starter panel. The load would be destroyed since resistors can only take so much voltage before burning out. Other components on the panel could be damaged too. It is important to protect current transformers from high voltage on their secondary side because they are often used as remote sensors for power lines.